1H-pyrazolo[5,1-c][1,2,4]triazole (named in accordance with the IUPAC nomenclature, and also sometimes called 1H-pyrazolo[3,2-c]-s-triazole) compounds are compounds useful as couplers, particularly as magenta couplers, for photographic materials and are described, for example, in British Patent No. 1,252,418, U.S. Pat. No. 3,725,067, and Journal of the Chemical Society, Parkin I, 2047 (1977).
Early processes for the preparation of these compounds are described in the above-mentioned patents and literature and Research Disclosure, Vol. 124, No. 12443 (1977). Typical processes thereof can be illustrated by the following reaction schemes: ##STR2##
In the above early synthesis processes, R was limited to an alkyl group, an aryl group, or a heterocyclic group, and there was a restriction that the process could only be carried out by synthesizing first a coupler whose 7-position is unsubstituted (it is called a four-equivalent coupler) like 2, 3, 4, and 5and by then synthesizing a coupler having a coupling releasing group (a group or an atom capable of being released upon a coupling reaction) (it is called a two-equivalent coupler).
As a measure to solve the problems, or limitations for production, a method wherein a halogen is introduced previously in the 4-position, to synthesize a hydrazinopyrazole (the substituent corresponding to --COOC.sub.2 H.sub.5 of compound 4 is a halogen atom), and then a two-equivalent coupler is synthesized based on the above-mentioned process (1), is disclosed in JP-A ("JP-A" means unexamined published Japanese patent application) No. 249987/1986, although the method is applied only to a case wherein the coupling releasing group is a halogen. Compounds capable of being used in the method are disclosed, for example, in JP-A Nos. 249967/1986, 249968/1986, 249969/1986, 158260/1987, 195366/1987, 195367/1987, and 228066/1987. Owing to these patents, it has become possible to synthesize couplers wherein R can be replaced with various substituents and a halogen atom is introduced as a coupling releasing group a reaction by way of not forming a four-equivalent coupler. However, if a coupling releasing group other than halogen is to be introduced, there is still a problem that further steps are required.
As methods for introducing, in the 7-position of 1H-pyrazolo[5,1-c][1,2,4]triazole coupler, a group, besides a halogen, that is a coupling releasing group, a synthesis method, which is of an aryloxy releasable type, is disclosed in JP-B ("JP-B" means examined Japanese patent publication) No. 27411/1972, and a synthesis method, which is of a nitrogen atom releasable type, is disclosed in JP-A No. 99437/1984, but they are synthesis methods wherein four-equivalent couplers or halogen (bromine) atom releasable two-equivalent couplers are involved and their yields are unsatisfactory.
When a coupler is introduced in a photographic system, the choice of the coupling releasing group is quite important to control the color-forming property and to improve the stability. Among couplers, two-equivalent 1H-pyrazolo[5,1-c][1,2,4]triazole magenta couplers, wherein the coupling releasing group is an aryloxy group, an alkoxy group, a heterocyclic oxy group, or an azolyl group, have such advantages that (1) their activity is high and (2) yellow stain does not occur even when processed with a stabilizing bath containing formalin, in comparison with couplers wherein the coupling releasing group is a halogen atom, and therefore the former are more useful than the latter wherein the coupling releasing group is a halogen atom. However, such two-equivalent couplers have the above-mentioned problems involved in their synthesis and they are not suitable to be produced industrially.
This is mainly because there has not been a suitable synthesis process or a proper intermediate to be used therein for synthesizing 1H-pyrazolo[5,1-c][1,2,4]triazoles that have such a group capable of being released upon coupling reaction.